Ordinary Democrat going through unimagined nightmare (6)
I believe the answer is:
ordeal
'nightmare' is the definition.
(nightmare can mean an ordeal or difficulty)
'ordinary democrat going through unimagined' is the wordplay.
'ordinary' becomes 'O' (abbreviation e.g. O-Levels).
'democrat' becomes 'd'.
'going through' is an insertion indicator.
'unimagined' becomes 'real' (I've seen this in another clue).
'd' inserted within 'real' is 'rdeal'.
'o'+'rdeal'='ORDEAL'
(Other definitions for ordeal that I've seen before include "Severly trying experience" , "very hard test" , "A tough time or hardship" , "A test of endurance or or difficult experience" , "Torture" .)